Keeping the specs simple definitely helps. My first experience of playing an FPS game against internet people was Red Crucible 2- there were certainly better games, but that one would work on my low-end laptop and poor internet (I might even have been using a dongle at that point), and it was browser playable through Kongregate and Facebook. Because it was accessible, I played that rather than better games, and obviously, non-gamers are less likely to have high-spec systems so that's a good point to think about.
Good luck with the social media. I'm waiting til we've got at least a beta demo for our next game before I brave that rabbit hole again!